1. Field of the Invention
The present invention relates to an airbag employed in a vehicle such as an automobile, an airplane or the like, and in particular to an airbag which is formed in a 3-dimensional shape and which has a large volume optimal for a front passenger seat of an automobile.
2. Description of the Related Art
In general, an airbag apparatus is structured such that an airbag and an inflator are accommodated in a module equipped in a vehicle interior equipment: and the airbag is inflated or expanded inwards a vehicle compartment by gas ejected from the inflator to protect a vehicle occupant. As the vehicle interior equipment, there are listed a center pad of the steering wheel, an instrument panel, a door trim, a seat and the like.
Particularly, regarding an airbag for a front passenger seat, since an instrument panel and an occupant or a passenger are distanced from each other, the airbag is required to have a large volume when it is inflated and to inflate or develop in a 3-dimensional or cubic shape to protect an occupant.
As such an airbag for a front passenger seat, there is one which has been disclosed in Japanese Patent Application Laid-Open No.10-315892. This airbag has a base cloth structure comprising three base cloths of a pair of side base cloths and a main base cloth. However, in the airbag comprising three base cloths, there is a drawback that sewing work is complicated and workability is deteriorated due to increase in the number of parts and necessity of 3-demensional sewing.
In view of such a drawback, there has been proposed another airbag such as shown in FIG. 1 and as disclosed in Japanese Patent Application Laid-Open No.9-99795. An airbag as disclosed in that publication is formed such that two upper and lower base cloths (fabrics) B and C are put one on another and peripheral portions thereof are joined through sewing or the like. That arrangement has an advantage in that the number of parts is reduced and workability is improved.
In such a conventional airbag A, however, since the upper and lower base cloths B and C are set to the same shape, there is a possibility that, when the airbag A is inflated, a space or gap occurs between the inflated or expanded airbag and the abdomen H1 of a vehicle occupant H. Also, as shown in FIG. 2, there is a possibility that, when the occupant H sits on a front side seat and he/she abuts on the lower base cloth C, the airbag A is pressed by the breast H2 of the occupant H to be displaced in a direction G.